Circulating Biomarkers in Lower Extremity Artery Disease

Lower extremity artery disease (LEAD), a chronic condition with disturbed lower extremity circulation due to narrowing of the arteries, is predominantly caused by atherosclerosis and is associated with the presence of cardiovascular risk factors and an increased risk of cardiovascular events. LEAD is prevalent among older individuals and predicted to rise with the ageing population. In progressive disease, the patient experiences symptoms of ischaemia when walking and, in advanced critical limb-threatening ischaemia, even at rest. However, LEAD is asymptomatic in most patients, delaying diagnosis and treatment. In this setting, circulating biomarkers may facilitate earlier diagnosis in selected individuals. This review provides a broad overview of the circulating biomarkers investigated to date in relation to LEAD and discusses their usefulness in clinical practice.

Role of genetics in peripheral arterial disease outcomes; significance of limb-salvage quantitative locus-1 genes

Peripheral artery disease is a major health care problem with significant morbidity and mortality. Humans with peripheral artery disease exhibit two major and differential clinical manifestations - intermittent claudication and critical limb ischemia. Individuals with intermittent claudication or critical limb ischemia have overlapping risk factors and objective measures of blood flow. Hence, we hypothesized that variation in genetic make-up may be an important determinant in the severity of peripheral artery disease. Previous studies have identified polymorphism in genes, contributing to extent of atherosclerosis but much less is known about polymorphisms associated with genes that can influence peripheral artery disease severity. This review outlines some of the progress made up-to-date to unravel the molecular mechanisms underlining differential peripheral artery disease severity. By exploring the recovery phenotype of different mouse strains following experimental peripheral artery disease, our group identified the limb salvage-associated quantitative trait locus 1 on mouse chromosome 7 as the first genetic modifier of perfusion recovery and tissue necrosis phenotypes. Furthermore, a number of genes within LSq-1, such as ADAM12, IL-21Rα, and BAG3 were identified as genetic modifiers of peripheral artery disease severity that function through preservation of endothelial and skeletal muscle cells during ischemia. Taken together, these studies suggest manipulation of limb salvage-associated quantitative trait locus 1 genes show great promise as therapeutic targets in the management of peripheral artery disease. Impact statement Peripheral artery disease (PAD) is a major health care problem with significant morbidity and mortality. Individuals with similar atherosclerosis burden do display different severity of disease. This review outlines some of the progress made up-to-date in unraveling the molecular mechanisms underlining differential PAD severity with a focus on the role of the Limb Salvage-associated Quantitative trait locus 1 (LSq-1), a key locus in adaptation to ischemia in PAD.

Systematic Review and Meta-Analysis of the Association Between C-Reactive Protein and Major Cardiovascular Events in Patients with Peripheral Artery Disease

BACKGROUND

Patients with peripheral artery disease (PAD) are at substantial risk of cardiovascular events. There is interest in using blood markers, such as C-reactive protein (CRP), to monitor prognosis and treatment efficacy in PAD patients. The aim of this meta-analysis was to assess the association between CRP and major cardiovascular events in PAD patients.

METHOD

Studies evaluating the association between CRP and major cardiovascular events (myocardial infarction, stroke, cardiac revascularisation and mortality) were identified using MEDLINE and the Cochrane library. Studies that did not include participants with PAD, measure CRP, or follow-up patients for cardiovascular events were excluded. Meta-analyses of published adjusted hazard ratios (HR) were conducted using an inverse variance-weighted random effects model, and heterogeneity was assessed with the I² index.

RESULTS

A total of 16 studies involving 5041 participants met the inclusion criteria for the systematic review. Eight studies were included in the meta-analyses. Summary effect estimates were reported as HR comparing higher and lower quantiles, and HR per unit increase in log_eCRP. PAD patients with higher CRP had a significantly greater risk of major cardiovascular events compared with those with lower CRP (HR 2.26, 95% CI 1.65-3.09, p < 0.001). The HR for major cardiovascular events was 1.38 (95% CI 1.16-1.63, p < 0.001) per unit increase in log_eCRP.

CONCLUSIONS

The present findings suggest that high circulating CRP is predictive of major cardiovascular events in PAD patients.

Carotid arterial wall inflammation in peripheral artery disease is augmented by type 2 diabetes: a cross-sectional study

Background

Patients with peripheral artery disease (PAD) are at increased risk of secondary events, which is exaggerated in the presence of type 2 diabetes mellitus. Diabetes is associated with a systemic pro-inflammatory state. We therefore investigated the cumulative impact of PAD and type 2 diabetes on carotid arterial wall inflammation. As recent data suggest a detrimental role of exogenous insulin on cardiovascular disease, we also included a group of insulin users.

Results

¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) imaging showed increased carotid arterial wall inflammation, assessed as target-to-background ratio (TBR), in PAD patients without diabetes (PAD-only: n = 11, 1.97 ± 0.57) compared with matched controls (n = 12, 1.49 ± 0.57; p = 0.009), with a significant further TBR increase in PAD patients with type 2 diabetes (PAD-DM, n = 23, 2.90 ± 1, p = 0.033 vs PAD-only). TBR of insulin users (n = 12, 3.31 ± 1.14) was higher compared with patients on oral medication only (n = 11, 2.44 ± 0.76, p = 0.035), despite comparable PAD severity (Fontaine stages), BMI and CRP. Multivariate regression analysis showed that Hba1c and plasma insulin levels, but not dose of exogenous insulin, correlated with TBR.

Conclusions

Concurrent diabetes significantly augments carotid arterial wall inflammation in PAD patients. A further increase in those requiring insulin was observed, which was associated with diabetes severity, rather than with the use of exogenous insulin itself.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0397-x) contains supplementary material, which is available to authorized users.

Biomarkers and Genetics in Peripheral Artery Disease

BACKGROUND

Peripheral artery disease (PAD) is highly prevalent and there is considerable diversity in the initial clinical manifestation and disease progression among individuals. Currently, there is no ideal biomarker to screen for PAD, to risk stratify patients with PAD, or to monitor therapeutic response to revascularization procedures. Advances in human genetics have markedly enhanced the ability to develop novel diagnostic and therapeutic approaches across a host of human diseases, but such developments in the field of PAD are lagging.

CONTENT

In this article, we will discuss the epidemiology, traditional risk factors for, and clinical presentations of PAD. We will discuss the possible role of genetic factors and gene-environment interactions in the development and/or progression of PAD. We will further explore future avenues through which genetic advances can be used to better our understanding of the pathophysiology of PAD and potentially find newer therapeutic targets. We will discuss the potential role of biomarkers in identifying patients at risk for PAD and for risk stratifying patients with PAD, and novel approaches to identification of reliable biomarkers in PAD.

SUMMARY

The exponential growth of genetic tools and newer technologies provides opportunities to investigate and identify newer pathways in the development and progression of PAD, and thereby in the identification of newer biomarkers and therapies.

The role of inflammation in cardiovascular diseases: the predictive value of neutrophil-lymphocyte ratio as a marker in peripheral arterial disease

Peripheral arterial disease (PAD) is an important manifestation of atherosclerosis, with increasing prevalence worldwide. A growing body of evidence shows that the systemic inflammatory response is closely related to the development, progression, and prognosis of atherosclerosis. In the last decade, several studies have suggested the role of measured inflammatory biomarkers as predictors of severity and prognosis in PAD in an effort to stratify the risk of these patients, to improve treatment selection, and to predict the results after interventions. A simple inflammatory marker, more available than any other, is the neutrophil-lymphocyte ratio (NLR), which can be easily obtained in clinical practice, based on the absolute count of neutrophils and lymphocytes from the differential leukocytes count. Many researchers evaluated vigorously the NLR as a potential prognostic biomarker predicting pathological and survival outcomes in patients with atherosclerosis. In this work, we aim to present the role of NLR as a prognostic marker in patients with PAD through a thorough review of the literature.

Risk factors for thromboembolism and pulmonary artery hypertension following splenectomy in children with hereditary spherocytosis

BACKGROUND

The aim was to study risk-factors for vascular thrombosis and incidence of pulmonary artery hypertension (PAH) in splenectomized children with hereditary spherocytosis (HS) at a single center.

PROCEDURE

Pre- and post-splenectomy hemoglobin and platelet counts were recorded. Post-splenectomy lipid-profile, fibrinogen, D-dimer, CRP and anti-coagulant-protein levels were compared to established controls. Echo-Doppler was performed for PAH.

RESULTS

Twenty-six children with HS had undergone splenectomy; the mean age at surgery was 7.9 ± 3.7 years. Nineteen of the 26 were prospectively investigated at a median duration of 4.5 years (range: 4 months to 19 years) following splenectomy. Thrombocytosis was observed in 19 (73%), whereas no patient had erythrocytosis at the last follow-up visit. Total cholesterol, LDL-C, HDL-C, and triglyceride levels were not deranged (P ≥ 0.3). Mean CRP levels (males: 2.8 ± 0.5; females: 2.1 ± 0.5 mg/L) were significantly higher than described for normal children (P < 0.001). Six (23%) patients had a positive D-dimer assay. Protein S, anti-thrombin-III and fibrinogen were in range. A single patient had a borderline low protein C activity. Lupus anticoagulant and anti-cardiolipin antibody assays were negative. The mean tricuspid regurgitant jet velocity (TRJV) was 1.8 ± 0.55 meter per second (range: 0-2.4). None had a TRJV ≥2.5 meter per second to suggest PAH.

CONCLUSIONS

There was no evidence of PAH, dyslipidemia, elevation of fibrinogen or a reduction in anti-coagulant proteins, at a median follow-up duration of 4.5 years following splenectomy in children with HS. However, elevated CRP level (42%), persistent thrombocytosis (73%) and elevated D-dimer levels (23%) were observed. These have been recognized as risk factors for cerebrovascular and coronary heart disease.

Effect of filarial infection on serum inflammatory and atherogenic biomarkers in coronary artery disease (CURES-121)

Helminth infections can potentially confer protection against metabolic disorders, possibly through immunomodulation. In this study, the baseline prevalence of lymphatic filariasis (LF) among subjects without (N = 236) and with (N = 217) coronary artery disease (CAD) was examined as part of the Chennai Urban Rural Epidemiological Study (CURES). The prevalence of LF was not significantly different between CAD(-) and CAD(+) subjects. The LF antigen load and antibody levels indicated comparable levels of infection and exposure between the groups. Within the CAD group, LF(+) and LF(-) subjects had no significant difference in the intimal medial thickness and high-sensitivity C-reactive protein values. However, LF infection was associated with augmented levels of tumor necrosis factor-α and interleukin-6 among CAD(+) subjects. The LF infection had no effect on serum adipocytokine profile. In conclusion, unlike type-2 diabetes, there is no association between the prevalence of LF and CAD and also no evidence of protective immunomodulation of LF infection on CAD in the Asian Indian population.